1. Field of the Invention
The present invention relates in general to audio data processing and in particular, methods for surround sound simulation and circuits and systems using the same.
2. Description of the Related Art
The ability to process audio information has become increasingly important in the personal computer (PC) environment. Among other things, audio is important in many multimedia applications, such as gaming and telecommunications. Audio functionality is therefore typically available on most conventional PCs, either in the form of an add-on audio board or as a standard feature provided on the motherboard itself. In fact, PC users increasingly expect not only audio functionality but high quality sound capability. Additionally, digital audio plays a significant role outside the traditional PC realm, such as in compact disk players, VCRs and televisions. As the audio technology progresses, digital applications are increasingly sophisticated as improvements in sound quality and sound effects are sought.
One of the key components in many digital audio information processing systems is the decoder. Generally, the decoder receives data in a compressed form and converts that data into a decompressed digital form. The decompressed digital data is then passed on for further processing, such as filtering, expansion or mixing, conversion into analog form, and eventually conversion into audible tones. In other words the decoder must provide the proper hardware and software interfaces to communicate with the possible compressed (and decompressed) data sources, as well as the destination digital and/or audio devices. In addition, the decoder must have the proper interfaces required for overall control and debugging by a host microprocessor or microcontroller. Since, there are a number of different audio compression/decompression formats and interface definitions, such as Dolby AC-3 and S/PDIF (Sony/Phillips Digital Interface), a state of the art digital audio decoder should at least be capable of supporting multiple compression/decompression formats.
Another feature often demanded by the customer is the ability of an audio system to perform effects processing. For example, surround sound and reverberation processing are often important to the user since they allow recorded music to be replayed in a simulated concert hall environment. It would be a significant advantage if such effects processing capability could also be supported by the audio decoder chip.
A method of producing reverberation effects is disclosed. A filter is implemented for modeling early acoustic reflections in response to an input signal using a first processor, the filter including a delay buffer of a selected length and having a selected number of taps for tapping samples of corresponding amounts of delay and a summer for summing the tapped samples to generate a filter output signal. A reverberator is implemented for modeling late acoustic reflections using a second processor, the reverberator receiving the filter output and generating a plurality of output signals.
The principles of the present invention allow for the efficient support of audio effects processing in a multiprocessor environment. Among other things, the principles allow for surround sound and reverberation effects processing on a single chip audio decoder.